Method and device for reeling up in the proper position a hot-rooled strip in a reeling installation

ABSTRACT

The invention relates to a method and a device for the positionally correct winding up of a metal strip in a coiling device, the hot strip being fed to the coiling device by a driving device with driving rollers, the driving rollers being tiltable in relation to one another by a controller by means of actuators for changing the gap between the driving rollers, and the controller being fed the position of the edge of the hot strip upstream of the driving device as a measured variable and as a setpoint reference variable, an optimization of the winding result of the rolled strip coil being achieved by the surface geometry of the rolled strip being determined as a measured variable and fed to the controller.

[0001] The invention relates to a method for the positionally correctwinding up of a metal strip, in particular a rolled hot strip, in acoiling device, the hot strip being fed to the coiling device by adriving device with driving rollers, the driving rollers being tiltablein relation to one another by a controller by means of actuators forchanging the gap between the driving rollers and the resultantinfluencing of the lateral position of the hot strip, and the controllerbeing fed the position of the edge of the hot strip upstream of thedriving device as a measured variable and as a setpoint referencevariable, and claiming the priority of German Patent Application 100 14813.1-32, to the content of which reference is made.

[0002] Furthermore, the invention relates to a device for thepositionally correct winding up of a rolled hot strip in a coilingdevice, with a driving device with driving rollers feeding the hot stripto the coiling device, with actuators and a controller for them, forchanging the gap between the driving rollers and the resultantinfluencing of the lateral position of the hot strip, and with ameasuring device for determining the position of the edge of the hotstrip upstream of the driving device, the measured values of which arefed to the controller.

[0003] It is generally known that, in hot strip rolling, after it runsout of the last stand of the finishing train, the finish-rolled hotstrip is transported from the delivery table through a cooling line,preferably a system of spray-water nozzles, to a coiling device. The hotstrip is wound up by the coiling device into coils. In the regionupstream of the coiling device, the hot strip may be guided on thedelivery table by side guide shoes, which can be hydraulically adjustedlaterally onto the strip edges, in order to align the rolled hot stripfor running into the coiling device. In a corresponding way, the sideguide shoes are in contact with the strip edges of the hot strip duringthe coiling operation.

[0004] Arranged at the end of the delivery table is a driving device,which substantially comprises a lower driving roller, which is mountedin the frame of the coiling device, and an upper driving roller, whichis mounted in a driver rocking arm. The upper driving roller can bepivoted by means of hydraulic cylinders for setting and adjusting thegap between the driving rollers. With the aim of stabilizing the runningof the strip, convex lower driving rollers or else driving rollers witha cylindrical central part and respectively conical roller ends areprimarily used. The main functions of the driving device, including itsdrives, are to tension the beginning of the rolled strip coming from thefinishing train, direct the incoming tip of the strip in the directionof the coiling device and ensure the draw-back counter to the coilingdevice during the coiling operation.

[0005] The main components of the coiling device are an expandingmandrel for winding up the rolled strip, back-up rollers and guide traysfor guiding the rolled strip during the winding operation and also amandrel drive. The free mandrel end (coil drawing-off side) is generallysupported during coiling by a mandrel bearing which can be swung in.

[0006] To initiate the winding operation, the tip of the hot stripcoming from the finishing stand is deflected by the pair of drivingrollers from the plane of the delivery table downward toward the windingmandrel. Then, the back-up rollers and the guide trays of the coilingdevice pass the beginning of the strip several times around the rotatingmandrel. The mandrel comprises a number of segments, which arecontinuously expanded shortly after the tip of the strip arrives, untilthe strip is wound into lays of coil lying firmly one on top of theother with frictional engagement. The main functions of the coilingdevice are to ensure the frictional connection of the beginning of thestrip and the mandrel, to carry the coil produced during winding and toapply defined strip tension to the strip during the winding.

[0007] Furthermore, German Offenlegungsschrift DE 38 28 356 A1 alreadydiscloses a method for influencing the position of the hot strip whichis fed to a coiling device by a pair of driving rollers, and a drivingdevice for carrying out this method. In the case of this method ofcontrolling the strip position, the strip guidance for the coilingdevice takes place exclusively by an asymmetric adjustment of the gapbetween the driving rollers by means of a pivotable upper drivingroller. For this purpose, the upper driving roller is mounted in adriver rocking arm, which has hydraulic adjustment and balancing. Thisalso has the result that the side guide shoes are opened during thecoiling operation.

[0008] The adjusting effect of this driving device with respect to thehot strip is based on a shift in the location of the point of action ofthe strip tensioning force and the resultant uneven elastic striplengthening (bending) caused by pivoting of the upper driving roller.Pivoting of the upper roller leads to opening of the driver gap on oneside and consequently a shift in the point of action of the pressingforce which the driving rollers exert on the strip. The point of actionof the force, which in the case of a symmetrical driver gap lies in thecenter of the installation, is now shifted by a distance from the centerof the installation in the direction of the unopened side of the drivergap. As a consequence of this, the strip draw-back force resulting fromthe braking moment of the driving device likewise acts at a distancefrom the center of the installation on the strip which until then isstill running centrally. This force-introducing situation brought aboutby the pivoting/tilting of the upper driving roller results in a momentexerted on the still centrally running strip that causes elastictransverse bending of the strip. As a consequence of this deforming ofthe strip, the longitudinal fibers of the strip in the region of thedriving device are oriented at an angle in relation to the center axisof the installation or at an angle in relation to the axes of thedriving rollers. Consequently, a strip led in frictional engagement overa driving roller tends to follow the curves of the path of the points ofthe roller shell in the contact region. This means in the present casethat the strip does not for instance run through the driving device in apath following the longitudinal direction of the strip fibers, butinstead the point of the strip located at the given instant in thecontact region is transported in the direction of the circumferentialspeed vector of the roller at the contact point, that is in thedirection of the longitudinal axis of the installation. This results ina transverse shift of the strip in the driving device. This shift of thestrip also causes a gradual increase in the distance between the pointof action of the driver draw-back force and the center point of thetension on the coil at the strip run-on point. However, with greattilting of the upper driving roller, the distance from the center of theinstallation becomes considerably greater than the transverse shifts ofthe strip occurring, so that the influence of the resultant change inthe distance from the center of the installation can be ignored.

[0009] The strip position control system disclosed by the aforementionedGerman Offenlegungsschrift DE 38 28 356 A1 substantially comprises astrip edge detection system, a strip position controller and a hydraulicadjustment of the upper driving roller with force and tilt control. Theinfluencing of the strip position takes place by the pivoting/tilting ofthe upper driving roller in a way corresponding to the mechanicalprinciples described above. The system deviation for the strip positioncontroller is formed from the position of the strip edge at the giveninstant, which is detected by means of strip edge scanning, and thesetpoint position value, which is determined from the strip width andthe dimensions of the installation. The output variable of the stripposition controller is the setpoint value of the driving roller tilt,which is prescribed for the driving roller adjustment. Since no contactoccurs between the shoes and the strip when the side guide shoes areopen, both the customary wearing of the shoes and damage to the edges ofthe strip caused by the side guide shoes are avoided.

[0010] Operational tests have shown that strip guidance by the drivingdevice with the side guide shoes open is possible in principle for hotrolled strips up to a thickness of approximately 5 mm. However, thequality requirements for the wound state are not completely satisfiedwith this method. The contour of the coil end face showed limited butinadmissible residual undulations (range of variation around ±10 mm).During unthreading from the finishing stand, winding offsets occur. Thefollowing causes are decisive for these defects, i.e. for the lateralshearing out of lays of coil:

[0011] Essential for the function of the driving device as an actuatorfor the strip position controller is the influencing of the deliveryangle of the strip (angle between strip center line and driving rolleraxis). In the case of curved strips (“sabre form”), the angle caused bythe curvature has the effect of a disturbance, i.e. the angle from thestrip curvature is not taken into account when generating themanipulated variable and falsifies the latter in an initially undetectedmagnitude.

[0012] Since the armature current of the driving roller drives iscontrolled by the higher-level drive control, and can consequently alsobe limited, if a current limit that is too low is prescribed, theresultant tension in the strip between the mandrel and the drivingdevice is too low, so that the aimed-for actuating effect cannot beachieved by pivoting the upper driving roller in order to drive thestrip into the setpoint position.

[0013] An abrupt relaxation of the tension of the strip also takes placewhen the strip is unthreaded from the finishing stand, which can causeinstances of slippage in the driver gap and consequently cause a windingoffset in the coil.

[0014] Furthermore, a method for measuring the surface geometry of hotstrip by generating lines on the strip surface by means of a lightsource is described in German Patent DE 197 09 992 C1. This method isintended to make simple and effective detection of the flatness of thestrip possible, in order to use this for a more sensitive control ofrolling and coiling parameters. A pattern of lines is projected by meansof a slide projector on the measuring surface, the hot strip or the endface of a coil in the process of being produced, and is detected bymeans of a CCD camera (charge coupled device). The projector is in thiscase arranged above the hot strip and projects the pattern of lines atan angle to the vertical onto the surface of the hot strip, so that thelines preferably extend transversely in relation to the surface of thestrip and consequently cover the entire width of the strip.

[0015] The CCD camera detects the lines running transversely over thesurface of the strip. If the strip is absolutely flat, a uniform patternof straight lines with unchanged line spacing is produced. Deviations ofthe surface of the strip from the ideal plane cause a change in the linespacing in the region of the unevenness. This change is detected by thecamera and can be computationally converted in a simple way intodifferences in height by a comparison with a reference pattern. In a waysimilar to measuring flatness on the running strip, the measuring systemcan be used to monitor the flatness of the end faces during coiling. Theend face of the coil building up in the coiler in this case correspondsto the surface of the strip. This measuring method makes possible arapid online determination of the actual differences in height of thesurface of the strip and consequently allows real-time detection andcontrol of continuous portions of strip. This has the advantage that themeasurement results allow the rolling and/or coiling parameters to beadapted immediately after an unevenness occurs. Even a transverseconvexity of the strip can be determined in this way. Conventionalmeasuring systems detect only the fiber length of the strip. What ismore, the measuring lines can be adapted with respect to their intensityand line thickness to different conditions.

[0016] To sum up, it is consequently found that there continue to beoccurrences of lateral shearing out of lays of coil during the coilingup of rolled strip, which are caused by transverse movements of therolled strip to be coiled up and lead to uneven end faces of the coil.In the course of the further processing and transporting of such coils,the protruding strip edges are susceptible to damage. Owing to theseinstances of damage, additional costs may arise in further processing orlosses in revenue may occur. In addition, the conventional way,described at the beginning, of guiding the rolled strip during coilingby means of side guide shoes entails relatively high expenditure onmaintenance, since the side guide shoes are subject to increasedabrasive wear by the strip edges of the rolled strip to be guided.

[0017] The present invention is based on the object of providing amethod and a device for the positionally correct winding up of a hotstrip into a coiling device, with which an optimization of the windingresult of the rolled strip coil is achieved. It is primarily intendedfor instances of lateral shearing out of the individual lays of coil ofthe rolled strip during coiling to be avoided and for the wound coil tocorrespond to DIN requirements, such as firmly wound, as round aspossible and with straight edges. The limit dimensions for a coil in thewound state are specified in DIN 1016.

[0018] This object is achieved by a method for the positionally correctwinding up of a rolled hot strip in a coiling device by the surfacegeometry of the rolled strip being determined as a measured variable andfed to the controller. With respect to the device for the positionallycorrect winding up of a hot strip in a coiling device, this object isachieved by the arrangement of a measuring device for determining thesurface geometry of the rolled strip in the region upstream of thedriving device, the measured variable of which device is fed to thecontroller. Advantageous refinements of the method according to theinvention and the device are specified in the subclaims 2 to 6 and 8 to10.

[0019] The method according to the invention for the positionallycorrect winding up of a hot strip in a coiling device and its associateddevice can be designed in a multi-variable strip position control systemwith pilot control, that substantially comprises a measuring system fordetecting the surface geometry of the strip and the position of thestrip edge, a multi-variable controller for the strip tension and thestrip position, a pilot control, which takes into account the influenceof the surface geometry of the incoming strip, an observer forappraising the strip position on the coil and the strip tension betweenthe driver and the mandrel and also a hydraulic adjustment of the upperdriving roller by a force and tilt control.

[0020] The method for the positionally correct winding up of a hot stripinto a coiling device and its associated device can be advantageouslyretrofitted into existing installations by using the existing actuators(adjustment of the driving rollers, drives of the driving apparatus andmandrel) and the measuring device for determining the strip position andthe surface geometry of the strip. It is particularly advantageous thatthe reference variable for the strip tension of the driving device isdimensioned such that the complete takeover of the draw-back by thedriving device when the rolled strip is unthreaded from the last standof the finishing train does not take place abruptly, but instead asteadily differentiatable increase up to full takeover of the tensionalready takes place before the end of the strip is unthreaded from thefinishing stand. As a result, winding offsets in the coil aresuccessfully avoided.

[0021] The main advantages of the method and of the device according tothe invention are that the surface geometry of the strip in the entry tothe coiling device are predictively taken into account by a pilotcontrol, the position of the strip on the coil is appraised by observersusing verifiable physical models and the strip tension is optimized,taking into account the surface geometry of the incoming strip and thestrip position at the given instant.

[0022] The invention is explained in more detail below on the basis ofan exemplary embodiment of the represented in the drawing, in which:

[0023]FIG. 1 shows a side view of an end portion of a delivery tablewith an adjoining driving and coiling device for a hot strip,

[0024]FIG. 2 shows a view of a detail of the driving rollers of thedriving device and

[0025]FIG. 3 shows a block diagram of a control loop for amulti-variable control of the strip position of a hot strip in theregion of a coiling device.

[0026]FIG. 1 shows a schematic side view of an end portion of a deliverytable 1, which is connected on the input side to a finishing stand (notrepresented) of a hot strip train. On the delivery table 1, afinish-rolled hot strip 2 is transported in the direction of a coilingdevice 3 with an upstream driving device 4. The hot strip 2 can be woundup by the coiling device into coils 5. The driving device 4 arranged atthe end of the delivery table 1 substantially comprises a lower drivingroller 6 and an upper driving roller 7. The upper driving roller 7 canbe adjusted in the direction of the lower driving roller 6 and laterallytilted by hydraulic piston/cylinder units (not represented) for settingand adjusting the gap between the driving rollers 6 and 7. In FIG. 2,which is a view of a detail of the driving rollers 6 and 7 of thedriving device 4, a tilted upper driving roller 7 and a wedge-shapeddriving roller gap 17 are represented. The alignment of the incomingrolled strip 2 in the direction of the coiling device 3 exclusively onthe basis of the tilting adjustment of the driving rollers 6 and 7 inrelation to each other and the mechanical principles of the transversedisplacement of the hot strip in the driving roller gap which can bebrought about as a result has already taken place at length in theacknowledgement of German Offenlegungsschrift DE 38 28 356 A1, alreadycited at the beginning, which hereby becomes part of the description. Inaddition, to stabilize the running of the strip, the lower drivingroller 6 is convexly formed.

[0027] The driving device 4, including its drives that are notrepresented, has, in addition to the task described above of directingand aligning the incoming hot strip in the direction of the coilingdevice 3, the tasks of tensioning the beginning of the hot strip 2coming from the finishing train, directing the incoming tip of the stripin the direction of the coiling device 3 and ensuring the draw-back ofthe hot strip 2 counter to the coiling device 3 during the windingoperation.

[0028] The coiling device 3 substantially comprises a driven andexpanding mandrel 8 for winding up the rolled strip 2 and also, notrepresented, back-up rollers and guide trays for guiding the rolledstrip 2 during the winding operation. To initiate the winding operation,the tip of the hot strip 2 is deflected by the driving rollers 6 and 7from the plane of the delivery table 1 downward toward the windingmandrel 8. Then, the back-up rollers and the guide trays of the coilingdevice 3 pass the beginning of the strip several times around therotating mandrel, the segments of the mandrel 8 being continuouslyexpanded until the rolled strip 2 is wound into lays of coil lyingfirmly one on top of the other with frictional engagement. The mainfunctions of the coiling device 3 are to ensure the frictionalconnection of the beginning of the strip and the mandrel 8, to carry thecoil 5 produced during winding and to apply defined strip tension to thestrip 2 during the winding.

[0029] Furthermore, side guide shoes 11, which are arranged at therespective ends of the rollers 9 of the delivery table 1 and can beadjusted laterally onto the edges 10 of the hot strip 2, are provided inthe region of the end of the delivery table 1 in order to align thebeginning of the hot strip 2 for running into the coiling device 3. Theside guide shoes 11 are opened during the coiling operation.

[0030] Also arranged in the region of the end of the delivery table 1 isa measuring device 12 for determining the position of the edge of therolled strip 2 and also a further measuring device 13 for determiningthe surface geometry of the rolled strip 2, in particular for detectingany “sabre form” of the rolled strip 2. The measuring devices 12 and 13are preferably arranged upstream of the side guide shoes 11 anddownstream of the cooling line (not represented) in the path of thedelivery table 1. The measuring device 13 for determining the surfacegeometry of the rolled strip 2 has a projector 18 and a camera 19 andits function has already been explained in more detail at the beginningin connection with the acknowledgement of German Patent DE 197 09 992C1, which hereby becomes part of the description.

[0031]FIG. 3 shows a block diagram of a control loop for amulti-variable control of the strip position of a hot strip 2 in theregion of a coiling device 3. It is evident that the manipulatedvariables for the driving roller adjustment (setpoint driving rollertilting) and the driving roller drive (setpoint strip drawing moment)are determined with the aid of a multi-variable controller 14. In thiscase, the influence of the surface geometry of the strip, in particularthe so-called “sabre” form, is compensated by a pilot control 15. Forthis pilot control 15, a fictitious transverse bending moment isdetermined from the result of the strip surface geometry measurement 13and the strip tension and is compensated by corresponding tilting of theupper driving roller 6, to avoid the rolled strip 2 being drivenlaterally on account of the surface geometry of the strip.

[0032] The strip position on the coil, for the measurement of which sofar no methods that can be realized in rolling operation are known, andthe strip tension between the driving device 5 and the mandrel 8 areappraised with the aid of observers 16 (model-aided determination ofnon-measurable variables from measured variables) and fed back forforming the system deviations. For this purpose, the position of thestrip edge upstream of the driver is determined by means of themeasuring device 12.

[0033] As reference variables, the setpoint strip edge position and thesetpoint strip tension are fed to the multi-variable controller 14. Thereference variable for the strip tension of the driving device 5 isdesigned such that the complete takeover of the draw-back by the drivingdevice 5 when the rolled strip 2 is unthreaded from the last stand ofthe finishing train does not take place abruptly, but instead theretakes place a steadily differentiatable increase up to full takeover ofthe tension that already begins before the end of the strip isunthreaded.

[0034] The rotational speed of the driving rollers (6, 7), the fieldcurrent and the field voltage and the armature current and the armaturevoltage of the motors driving the driving rollers (6, 7), the pressingforce of the driving rollers and the bending moment of the strip aroundthe driving rollers are preferably used for the model-aideddetermination (observers 16) of the actual strip tension.

[0035] The strip tension, the driving roller tilt, strip speed, stripposition upstream of the driver and surface geometry of the rolled stripare preferably used for the model-aided determination (observers 16) ofthe actual position of the strip edges.

[0036] The control of the drive of the mandrel 8 takes place by arotational speed control with secondary torque and current control. Tocontrol the motor torques, the specific strip data are prescribed. Thisachieves the effect that the strip tension is adapted to the strip crosssection and is constant over the length of the strip. The control of thedrives of the driving rollers 6 and 7 takes place by a speed controlwith secondary current control. The hydraulic adjustment of the upperdriving roller 7 takes place by a force and tilt control.

1. A method for the positionally correct winding up of a metal strip ina coiling device, the metal strip, in particular rolled hot strip, beingfed to the coiling device by a driving device with driving rollers, thedriving rollers being tiltable in relation to one another by acontroller by means of actuators for changing the gap between thedriving rollers, and the controller being fed the position of the edgeof the metal strip upstream of the driving device as a measured variableand as a setpoint reference variable, characterized in that the surfacegeometry of the metal strip (2) is determined as a measured variable andfed to the controller (14).
 2. The method as claimed in claim 1,characterized in that the determined surface geometry of the hot strip(2) is fed to a pilot control (15), which is arranged downstream of thecontroller (14) and upstream of the activation of the actuators of thedriving rollers (6, 7) for changing the driving roller gap (17).
 3. Themethod as claimed in claim 1 or 2, characterized in that the surfacegeometry of the hot strip (2) is determined before the feeding of thehot strip (2) to the driving device (4).
 4. The method as claimed in oneof claims 1 to 3, characterized in that the controller designed as amulti-variable controller (14) is fed the setpoint strip tension betweenthe driving rollers (6, 7) and the coiling device (3) as a furtherreference variable and the driving roller drive and the setting of thedriving roller gap (17) are hereby activated by the controller (14). 5.The method as claimed in claim 4, characterized in that the setpointstrip tension is changed in such a preselected manner that, before thehot rolled stock is unthreaded from a finishing stand arranged upstreamof the driving device (4), the draw-back force of the driving rollers(6, 7) for the metal strip (2) wound up by the coiling device (3) issteadily increased up to full takeover of the drawback force afterunthreading of the metal strip (2).
 6. The method as claimed in claim 4or 5, characterized in that the actual strip tension between the drivingrollers (6, 7) and the coiling device (3) is determined by a model-aideddetermination of measurable variables and is fed to the multi-variablecontroller (14) as a measured variable.
 7. The method as claimed inclaim 6, characterized in that the rotational speed of the drivingrollers (6, 7), the field current and the field voltage and the armaturecurrent and the armature voltage of the motors driving the drivingrollers (6, 7), the pressing force of the driving rollers and thebending moment of the strip around the driving rollers are preferablyused for the model-aided determination (observers 16) of the actualstrip tension.
 8. The method as claimed in one of claims 1 to 7,characterized in that the actual position of the strip edges of thestrip wound up by the coiling device (3) is determined by a model-aideddetermination (observers 16) of measurable variables and is fed to themulti-variable controller as a measured variable.
 9. The method asclaimed in claim 8, characterized in that the strip tension, the drivingroller tilt, strip speed, strip position upstream of the driver andsurface geometry of the rolled strip are preferably used for themodel-aided determination (observers 16) of the actual position of thestrip edges.
 10. The method as claimed in one of claims 1 to 9,characterized in that the driving roller gap (17) is set by means of aforce and tilt control of the driving rollers (6, 7).
 11. A device forthe positionally correct winding up of a metal strip, in particular arolled hot strip, in a coiling device, in particular for carrying out amethod as claimed in claims 1 to 10, with a driving device with drivingrollers, tiltable in relation to one another, feeding the hot strip tothe coiling device, with actuators and a controller for them, forchanging the gap between the driving rollers and the resultantinfluencing of the lateral position of the hot strip, and with ameasuring device for determining the position of the edge of the hotstrip upstream of the driving device, the measured values of which arefed to the controller, characterized in that a measuring device (13) fordetermining the surface geometry of the rolled strip (2) is arranged inthe region upstream of the driving device (4), the measured variable ofwhich device is fed to the controller (14).
 12. The device as claimed inclaim 11, characterized in that the controller is designed as amulti-variable controller (14), to which the setpoint strip edgeposition and the setpoint strip tension are fed.
 13. The device asclaimed in claim 7 or 12, characterized in that the controller (14) islinked with an observer module (16), by which the actual strip tensionbetween the driving rollers (6, 7) and the coiling device (3) can bedetermined on a model-aided basis from measurable variables.
 14. Thedevice as claimed in one of claims 11 to 13, characterized in that thecontroller (14) is linked with an observer module (16), by which theactual position of the strip edges (9) of the strip (2) wound up by thecoiling device (3) can be determined on a model-aided basis frommeasurable variables.